1 files changed, 14 insertions, 19 deletions
diff --git a/Swiften/Network/DomainNameServiceQuery.cpp b/Swiften/Network/DomainNameServiceQuery.cpp
index f7ffecc..da1e1ab 100644
--- a/Swiften/Network/DomainNameServiceQuery.cpp
+++ b/Swiften/Network/DomainNameServiceQuery.cpp
@@ -2,68 +2,63 @@
  * Copyright (c) 2010 Remko Tronçon
  * Licensed under the GNU General Public License v3.
  * See Documentation/Licenses/GPLv3.txt for more information.
  */
 
 #include <Swiften/Network/DomainNameServiceQuery.h>
 
 #include <numeric>
 #include <cassert>
+#include <functional>
+#include <iterator>
 
 #include <Swiften/Base/RandomGenerator.h>
 #include <boost/numeric/conversion/cast.hpp>
 
 using namespace Swift;
 
 namespace {
 	struct ResultPriorityComparator {
 		bool operator()(const DomainNameServiceQuery::Result& a, const DomainNameServiceQuery::Result& b) const {
 			return a.priority < b.priority;
 		}
 	};
 
-	struct WeightAccumulator {
-			int operator()(int accumulator, const DomainNameServiceQuery::Result& result) {
-				return accumulator + result.weight;
-			}
-	};
+	struct GetWeight {
+			GetWeight() {}
 
-	struct WeightToProbability {
-			WeightToProbability(int total) : total(total) {}
-
-			double operator()(const DomainNameServiceQuery::Result& result) {
-				return result.weight / boost::numeric_cast<double>(total);
+			int operator()(const DomainNameServiceQuery::Result& result) {
+				return result.weight + 1 /* easy hack to account for '0' weights getting at least some weight */;
 			}
-			int total;
 	};
 }
 
 namespace Swift {
 
 DomainNameServiceQuery::~DomainNameServiceQuery() {
 }
 
 void DomainNameServiceQuery::sortResults(std::vector<DomainNameServiceQuery::Result>& queries, RandomGenerator& generator) {
 	ResultPriorityComparator comparator;
 	std::sort(queries.begin(), queries.end(), comparator);
 
 	std::vector<DomainNameServiceQuery::Result>::iterator i = queries.begin();
 	while (i != queries.end()) {
 		std::vector<DomainNameServiceQuery::Result>::iterator next = std::upper_bound(i, queries.end(), *i, comparator);
 		if (std::distance(i, next) > 1) {
-			int weightSum = std::accumulate(i, next, 0, WeightAccumulator());
-			std::vector<double> probabilities;
-			std::transform(i, next, std::back_inserter(probabilities), WeightToProbability(weightSum > 0 ? weightSum : 1));
-
-			// Shuffling the result array and the probabilities in parallel
-			for (size_t j = 0; j < probabilities.size(); ++j) {
-				int selectedIndex = generator.generateWeighedRandomNumber(probabilities.begin() + j, probabilities.end());
+			std::vector<int> weights;
+			std::transform(i, next, std::back_inserter(weights), GetWeight());
+			for (size_t j = 0; j < weights.size() - 1; ++j) {
+				std::vector<int> cumulativeWeights;
+				std::partial_sum(weights.begin() + j, weights.end(), std::back_inserter(cumulativeWeights));
+				int randomNumber = generator.generateRandomInteger(cumulativeWeights.back());
+				int selectedIndex = std::lower_bound(cumulativeWeights.begin(), cumulativeWeights.end(), randomNumber) - cumulativeWeights.begin();
 				std::swap(i[j], i[j + selectedIndex]);
-				std::swap(probabilities.begin()[j], probabilities.begin()[j + selectedIndex]);
+				std::swap(weights.begin()[j], weights.begin()[j + selectedIndex]);
 			}
 		}
 		i = next;
 	}
 }
 
 
 }